This invention relates to methods and devices for end-rounding bristles and filaments that are used to make bristles.
Conventional toothbrushes generally include tufts of bristles mounted on the head of an oral brush handle. The working ends (i.e.xe2x80x94the end that contacts the teeth and gums) of the bristles generally must be smoothed to remove sharp edges that might cut or irritate the gums. This process is known as end-rounding.
In most end-rounding methods, the working ends of the bristles are contacted with a sanding disc. Generally, these sanding discs are rotated using an electric motor. The size and weight of an electric motor generally makes it impractical to move the end-rounder.
The present invention features methods and devices for end-rounding bristles or continuous filaments that are used to make bristles.
In some implementations, the end-rounding device is movable into and out of contact with the filament ends, so that the filaments can be continuously fed in a single axial direction, without the bending and stress associated with moving the filaments into and out of contact with the end-rounder. Specifically, the end-rounder is moved into and out of position below the axial path of the ropes that eventually are cut into bristles.
The end-rounding device is air driven, light and has a low profile. The end-rounding device also has an ever-changing elliptical path, which attacks the bristles from all sides, producing a well-rounded bristle.
In one aspect, the invention features a device for end-rounding bristles including a sanding wheel mounted to a pneumatically driven support.
Some implementations include one or more of the following features. The pneumatically driven support includes a turbine. The pneumatically driven support includes a planetary drive mechanism that is driven by rotation of the turbine. The planetary drive mechanism includes a planet gear rotatably mounted on the pneumatically driven support and a fixed ring gear in engagement with the planet gear.
In another aspect, the invention features an end-rounding device that is less than about 2 inches in height. Preferably, the device weighs less than 5 pounds.
In another aspect, the invention features an end-rounding device having a planetary drive mechanism that is constructed to move the sanding wheel in an elliptical path.
Some implementations include one or more of the following features. The elliptical path is varied. The tooth ratio of the ring gear to the planet gear is about 2:1. The tooth ratio of the ring gear to the planet gear is slightly greater than 2:1. The pneumatically driven support is constructed to rotate at up to 5,000 revolutions per minute. The pneumatically driven support is constructed to rotate at up to 10,000 revolutions per minute. The sanding wheel is mounted on the pneumatically driven support so the center of the sanding wheel is within the pitch circle defined by the planet gear.
In another aspect, the invention features a sanding wheel and a planetary drive mechanism constructed to move the sanding wheel in an elliptical path. The planetary drive mechanism includes a planet carrier, a planet gear mounted on the planet carrier and a stationary ring gear wherein the planet gear engages the stationary ring gear and the planet carrier drives the planet gear. The tooth ratio of the stationary ring gear to the planet gear is slightly less than 2:1. The sanding wheel is mounted to the planet gear. The sanding wheel is mounted within a pitch circle defined by the planet gear. The planet carrier is pneumatically driven. The planet carrier is a turbine. The device is constructed to vary the direction of the elliptical path during rotation of the sanding wheel.
In a further aspect, the invention includes a feeding device constructed to advance a plurality of filaments through the machine in an axial direction and an end-rounding device constructed to be moved transversely relative to the axial direction, back and forth between a first position in which the end-rounding device is in contact with free ends of the filaments, and a second position in which the end-rounding device is not in contact with the free ends of the filaments.
In still another aspect, the invention features a method for end-rounding bristles including contacting the ends of bristles with an end-rounding device having a sanding wheel, the end-rounding device being constructed to move the sanding wheel in an elliptical path. Preferably, the end-rounding device includes a planetary drive mechanism and the planetary drive mechanism is pneumatically driven.
In another aspect, the invention features a method for end-rounding bristles including contacting ends of bristles with an end-rounding device including a sanding wheel and a pneumatically driven support for the sanding wheel.
Other features and advantages of the invention will be apparent from the description and drawings, and from the claims.